[billdaman]

Hello, haven’t posted in years, as my Volt has been relatively trouble free over 70K miles. The Volt sat for almost two years of the COVID lockdown as I didn't need it for my commute. After we returned to work, my work location is a 2 mile drive. The battery never depletes.

From what I’m reading here it appears all Volt owners will face a day of mourning when the battery gets to EOL and battery replacements are either impractical or cost prohibitive.

My question to the group is that of all the Variables linked to battery health, has anyone uncovered a specific set of criteria other than cell voltage differences to indicate a battery entering its down hill slide? It would be great to know that sweet spot at which you should drive it to the dealer to trade. The retail values of these are still high.

I used my bidirectional scanner yesterday and this is the report. Perhaps I need to dig deeper to read the individual cells, but it appears that the software does it for you. Acceptable difference of .02V. Is there anything looking strange or do I have a very good condition battery for 9 years old?

 

[voltreg]

The likely test would be to watch cell voltages in real time while the car is being driven very hard in sport mode. One would be able to thus get a relative indication as to the variation in internal impedance of each cell. Ones that show voltage sags greater than the majority would be suspect. If they all follow together...you are good to go likely with a very good battery. I use the VX Nano to check on mine for bottom balance but have not yet had anybody drive the car in the aforementioned set up where I can monitor under heavy load. My 14 has been keeping very consistent at the depletion point with the cells tracking pretty close to each other.

 

[TYmrLutz]

The "live" test voltreg describes above is likely an accurate method to determine battery health. An alternative is to test pack voltage variance when depleted and let sit overnight. A weak cell will likely drop much more than others over time. If you measure delta under different conditions then compare results, you may get a better indication of overall pack health. A delta that remains consistently in the .02v range would be optimal, <.05 is good, >.10 poor. IIRC, a propulsion reduced error occurs at the .25v range. The danger is a weak cell can overheat when charging and GM engineers erred on the safe side to prevent problems. For older packs, some are using Mountain mode all the time to raise the minimum voltage before ICE ignition and preventing any week cell from ever dropping out. Your pack is happiest when plugged in.

 

[LANMAN]

Checking the cell voltages with just a couple miles of battery left is a much better indicator of battery health. My 2012 has been popping up Propulsion Power Reduced messages for more than a year now. I have learned to drive easy on the accelerator when the battery has just a few miles left, and to precondition the car on colder days. Fingers crossed that it will make it long enough for one of my EV reservations comes through before the battery bricks.

 

[billdaman]

The likely test would be to watch cell voltages in real time while the car is being driven very hard in sport mode. One would be able to thus get a relative indication as to the variation in internal impedance of each cell. Ones that show voltage sags greater than the majority would be suspect. If they all follow together...you are good to go likely with a very good battery. I use the VX Nano to check on mine for bottom balance but have not yet had anybody drive the car in the aforementioned set up where I can monitor under heavy load. My 14 has been keeping very consistent at the depletion point with the cells tracking pretty close to each other.

Thanks for the advice. I just got back from driving it in sport mode the way a teenager treats a rental. Even with an hour of on off full throttle I still managed to squeak out over 35 miles from a full charge. I was graphing all the cells while I was driving and after depletion.

They were all consistent voltages readings across the cells through out the hour drive. Wondering if I can assume all is well and a good battery?

Here’s the energy data at full depleted:

and the depleted cell voltages, VS where I started .
View attachment 175871

 

[Off Oil]

The system allows for greater variation during use under certain conditions, as previously relayed by WOPOnTour, so I don't bother about data collection while driving. I collect the charged and depleted cell levels quarterly as posted here:
2017 HV Battery Cell Data (Sharing)

Some trends I've noticed to date is the highest voltage cell when fully charged has been the lowest when fully depleted. Also my actual range is noticeably reduced by ~6+ miles over the 6 year period.

At the end of the day the biggest factor will be time. I'd trade it prior to the 10 year mark, if you don't want to drive it until the battery fails.

 

[billdaman]

The system allows for greater variation during use under certain conditions, as previously relayed by WOPOnTour, so I don't bother about data collection while driving. I collect the charged and depleted cell levels quarterly as posted here:
2017 HV Battery Cell Data (Sharing)

Some trends I've noticed to date is the highest voltage cell when fully charged has been the lowest when fully depleted. Also my actual range is noticeably reduced by ~6+ miles over the 6 year period.

At the end of the day the biggest factor will be time. I'd trade it prior to the 10 year mark, if you don't want to drive it until the battery fails.

So if all my fully charged cells are over 4V with the greatest difference between cells is + 20mV and then the battery is run until depleted / until forced ICE start, and the discharged cells are all 3.58 +10mV, then is my battery above average condition for an 8-9 year old Volt? It’s crazy, I never even thought about any of this previously, but now that I realize new cells are no longer made I’m thinking twice about keeping it.

BTW , it’s basically a one owner garage queen, rarely driven more that 4-6 miles a day and always on a charger when it’s parked for any length of time.

 

[Off Oil]

So if all my fully charged cells are over 4V with the greatest difference between cells is + 20mV and then the battery is run until depleted / until forced ICE start, and the discharged cells are all 3.58 +10mV, then is my battery above average condition for an 8-9 year old Volt? It’s crazy, I never even thought about any of this previously, but now that I realize new cells are no longer made I’m thinking twice about keeping it.

BTW , it’s basically a one owner garage queen, rarely driven more that 4-6 miles a day and always on a charger when it’s parked for any length of time.

I don't know what the "average" cell readings are for an 8-9 year old Volt. Neither does anyone else except GM, and they aren't sharing. I know the cell level thresholds which indicate an issue, which is in the Service Manual.

My advice to people is if you put on very few miles such as your use case, a regular gas car is the best choice, as it will have the best longevity/long-term costs. In your case I would personally either (1) sell it now while it's in good shape and buy a new regular gas car, or (2) drive it until it dies, at which point I would sell it for scrap value. Given the age, I'd go for #1 if the household finances were in good shape.

 

[wordptom]

Wikipedia says GM programmed the Gen 1 Volt to use ~65% of the full capacity for Electric Mode driving. Your energy usage display photo shows you drove 35.6 electric miles, 9.0 kWh Used. If that’s the normal kWh Used you get for a full charge when you drive beyond battery range, math says the current full capacity of the battery is 9.0/65% = 13.85 kWh, which is ~84% of the original 16.5 kWh full capacity, or ~16% degradation over the years. IOW, it would appear your Volt’s battery has lost some capacity over time.

All batteries lose capacity over time (GM warranty says the Gen 1 battery should not lose more than 30% in the first 10 years). If all cells lose their Ah capacity at the same rate, then they’ll remain fairly well balanced, but, of course, your kWh Used per full charge will decrease. It’s when some battery pack cells lose capacity faster than others that results in larger voltage differences when the battery is depleted... those 96 cell groups are connected in series, so each contributes the same amount of current flow to the battery’s power output. If the cells are balanced at the full charge level, then those cells that have lost more capacity (Ah) over time than the others will, of course, discharge faster, so that by the time the automatic "switch to gas" has taken place, the voltages of those cells will reflect the lower remaining capacity of those cells, and will be lower than the voltages of the cells that have lost less capacity.

 

[imanjunk1963]

@wordptom I too have been monitoring with similar math. And even after my battery rebalance update I still have only lost as I calculate about about 5% to 8% (sometimes I see 9.8 up to 10.2 kwh used, before software updates 10.2kwh used) on my 2014 at now 120k miles of which I drove at least 85%+ by EV only and always plugged in and half usage drained fully and half recharged from about 8 miles left based on my daily activities. As it seems 2014s have been very reliable only having changed the hatch shocks by caution, one of the breather thingies in engine which escapes me and 1 time software update for the battery rebalancing and sensor recalibration software upgrades as well as 3 tire changes, 5 oil changes, 1 time 3 coolant loop changes, electric drive oil change, driver side washer changer for that licking noise and NO brake changes yet. Life is good and hopefully holds out until the Equinox and/or Blazer EVs arrive! Hurry up GM!

 

[billdaman]

Question, are you saying that using 65% of full capacity in electric mode as specified on Wiki holds true even if your vehicle has had the battery rebalance update? I lost 5 miles distance from a full charge IMMEDIATELY after the update, and believe me I was not happy.

However, I also bought into the hype that the range readings from the display were just estimates. Well those “estimates” have remained fairly consistent since. Also, when I took that screenshot I drove it as hard as I have ever driven it in 9 years on that day and that was in sport mode. Should that type of driving make a difference in range? I was attempting to deplete it as fast as possible and get frustrated at how long it took!

If my battery is 16% degraded at 8 years is that above average, average, at or around the mean or below average for a 9 year old battery?

 

[imanjunk1963]

As I mentioned already for my 2014 with 120k miles of mostly 80+% EV miles and always plugged in still shows 10.2kwh usable of the 10.7kwh rated after the balance update noting before the rebalance update I was still getting about 10.5kwh. So in my mind that rate of degradation I am experiencing is good after nearly 10 years.

 

[billdaman]

As I mentioned already for my 2014 with 120k miles of mostly 80+% EV miles and always plugged in still shows 10.2kwh usable of the 10.7kwh rated after the balance update noting before the rebalance update I was still getting about 10.5kwh. So in my mind that rate of degradation I am experiencing is good after nearly 10 years.

Got it. Assuming your 80% EV driving are full charge and depletion daily? My volt used to experience that and my range was 40+. Then I went to 17 miles each way with a charger at work at which point for 3 years I never ran it to depletion.

Then COVID where the Volt stayed in the garage for over a year with only a handful of uses. Now I drive 3 miles to work, plug it in, return 3 miles home, plug in, repeat. I never run it to depletion. Does the battery need s e depletion cycles to increase capacity?

 

[hellsop]

Does the battery need s e depletion cycles to increase capacity?

It does. After many cycles of charging without depletion, the battery will start getting pessimistic about its range estimations without actually diminishing its capacity. A couple of full depletions will set it right though, and it will start more accurately predicting how far it actually can go. (I've a suspicion that it doesn't well account for battery conditioning power and similar "startup costs" when it's looking at its historical consumption per mile calculations and projecting from those how far it might get on a discharge cycle.)